1. Field of the Invention
The present invention relates to a method for transmitting a sequence of data to be transmitted. Even though the present invention is described below essentially with reference to a transmission of sensor data to an engine control unit, it is not limited to this application, but is always advantageously applicable when a sequence of data to be transmitted is to be secured, in particular when a continuous or frequent transmission of data takes place. In addition to transmitting sensor data of an internal combustion engine, other applications may be found in the generalized embedded field, such as in other control units in the automobile (body computer, driver assistance computer, . . . ) or in the case of applications outside the automotive sector which require either a permanent sensor communication (for example, fire alarm systems or the like) or a constant communication in general (not only with one participating sensor).
2. Background of the Invention
The task of an engine control unit of an internal combustion engine consists of calculating output variables for the actuators, such as fuel injector or ignition system, from a plurality of input signals, such as rotational speed, temperature or pressure. Thus, for a safe operation of the internal combustion engine controlled by the control unit, the input signals received by the control unit must be correct. For example, disruptions in the data transmission should be detectable.
Another aspect relates to a change of input signals for increasing performance (so-called tuning). For this purpose, the input signals are changed in a way that results in increased engine performance. For example, sensor values from pressure sensors (pressure scavenging in a common rail, air pressure in an intake manifold, etc.) may be artificially reduced so that the control unit responds by boosting pressure and thereby increasing performance.
Both a faulty transmission of data as well as the tuning entails considerable risks. For example, excessive temperatures, pressures and rotational speeds as well as excessive stress on the power train and the braking system may result in defects. Furthermore, a deterioration in the exhaust gas values may occur. For this reason, it is desirable to ensure a correct data transmission.
In this context, a method for a secure transmission of sensor data is described in Published German patent application document DE 10 2009 002 396 A1 in which the sensor data are transmitted with the aid of a MAC method (message authentication code). In order in this case to prevent replay attacks in which earlier values are recorded and retransmitted at a later point in time, the sensor data are augmented by individual additions, such as a time code or a random number previously ascertained by the control unit at the sensor. This has the disadvantage that the sensor must either have a highly accurate time source or must have the option of receiving data from the control unit.
It is desirable to have at ones disposal a method for a secure transmission of a sequence of data to be transmitted, in particular sensor data, which may also be used in conjunction with simple communication devices, such as sensors, which does not have these options.